Proceedings of the Combustion Institute最新文献_第3页

Influence of soot oxidation reaction time scale on soot break-through 煤烟氧化反应时间尺度对煤烟突破的影响

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105930

Gandolfo Scialabba , Antonio Attili , Heinz Pitsch

A previous Direct Numerical Simulation (DNS) study is extended to assess the influence of the soot oxidation reaction time scale on soot break-through in turbulent non-premixed flames. In such cases, soot is formed in rich regions and then pushed toward the flame, where it is often completely oxidized without escaping to the lean region and hence the environment. However, a fast relative drift of soot particles with respect to the oxidation layer paired with local flame extinction can lead to soot break-through (soot leakage), even when the total equivalence ratio is lean. These conditions are met when turbulence levels are sufficiently high, leading to a smoking flame behavior. The baseline configuration consists of a turbulent non-premixed temporal jet where significant soot break-through is observed due to local extinction and mixing. A soot oxidation Damköhler number is defined as the ratio of the flow and soot oxidation reaction time scales. A parametric variation of the soot oxidation Damköhler number is performed by varying the oxidation time scale, i.e., rescaling the soot oxidation rate coefficients, while keeping the flow time scale constant. The relative influence on soot break-through of OH and O₂-based soot oxidation reaction time scales at varying soot oxidation Damköhler numbers (

{Da}_{Ox,OH}

and

{Da}_{Ox, O_{2}}

) is quantified. Soot and gas-phase statistics are collected along Lagrangian trajectories to evaluate the relative impact of partial soot oxidation events. A modest change in peak soot mass is observed for both variations. An even smaller impact is found for soot mass break-through, which is only marginally affected by the soot oxidation reaction time scales, as it mainly occurs in regions with strong local extinctions. The results imply that, to capture soot break-through events in reduced-order models, an accurate description of local flame extinction is likely more important than the values of soot oxidation reaction rates.

本文扩展了前人的直接数值模拟（DNS）研究，以评估烟尘氧化反应时间尺度对湍流非预混火焰中烟尘突破的影响。在这种情况下，烟灰在富油地区形成，然后被推向火焰，在那里它通常被完全氧化，而不会逃逸到贫油地区，因此不会逃逸到环境中。然而，即使在总等效比较低的情况下，烟尘颗粒相对于氧化层的快速相对漂移与局部火焰熄灭相结合，也会导致烟尘突破（烟尘泄漏）。当湍流水平足够高时，这些条件就会满足，从而导致烟焰行为。基线配置由湍流非预混时间射流组成，其中由于局部消光和混合而观察到显著的煤烟突破。烟灰氧化Damköhler数定义为流量与烟灰氧化反应时间尺度之比。在保持流量时间尺度不变的情况下，通过改变氧化时间尺度，即重新调整烟灰氧化速率系数，实现烟灰氧化Damköhler数的参数变化。量化了不同烟灰氧化Damköhler值（DaOx，OH和DaOx，O2）下，OH和O2基烟灰氧化反应时间尺度对烟灰突破的相对影响。沿着拉格朗日轨迹收集烟尘和气相统计数据，以评估部分烟尘氧化事件的相对影响。观察到两种变化的峰值烟灰质量都有适度的变化。煤烟质量突破的影响更小，受煤烟氧化反应时间尺度的影响较小，主要发生在局部物种灭绝强烈的地区。结果表明，为了在降阶模型中捕捉煤烟突破事件，准确描述局部火焰熄灭可能比煤烟氧化反应速率值更重要。

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引用次数: 0

Constrained reduced-order modeling of reacting flows using bounded Gaussian process likelihoods: application to a furnace operating under MILD conditions 使用有界高斯过程似然的反应流的约束降阶建模：在轻度条件下运行的炉上的应用

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105846

Muhammad Azam Hafeez , Alberto Procacci , Axel Coussement , Alessandro Parente

This study explores the application of a novel constrained reduced-order modeling framework to analyze a furnace operating under Moderate and Intense Low-oxygen Dilution (MILD) combustion conditions. The methodology employs low-cost Singular Value Decomposition (lcSVD) with optimal sensor placement for data compression and reconstruction, followed by Gaussian Process Regression (GPR) with bounded likelihood functions – truncated Gaussian and beta distributions – to ensure physically admissible outputs in high-dimensional combustion simulations. We test these models by predicting the unexplored thermo-chemical states of three-dimensional CH₄/H₂ simulation samples, with varying equivalence ratio, fuel composition (ranging from pure methane to pure hydrogen), and air injector diameter. Results indicate that the beta likelihood constrains species mass fraction predictions to the

0

–

1

interval by construction, yielding higher accuracy for species with localized distributions. Meanwhile, the truncated Gaussian enhances robustness by respecting realistic thermo-chemical ranges, reducing the influence of outliers, and improving model reliability in sparse or noisy data regions. These models demonstrate computational efficiency and scalability while delivering high-accuracy, physically consistent predictions.

本研究探索了一种新的约束降阶建模框架的应用，以分析在中度和强烈低氧稀释（MILD）燃烧条件下运行的炉。该方法采用低成本的奇异值分解（lcSVD）和最佳传感器位置来进行数据压缩和重建，然后采用高斯过程回归（GPR）和有界似然函数（截断高斯分布和beta分布）来确保高维燃烧模拟中物理上可接受的输出。我们通过预测三维CH4/H2模拟样品未探索的热化学状态来测试这些模型，这些样品具有不同的当量比，燃料成分（从纯甲烷到纯氢）和空气喷射器直径。结果表明，β似然通过构造将物种质量分数预测限制在0-1区间内，对于局域分布的物种，预测精度较高。同时，截断的高斯分布通过尊重真实的热化学范围、减少异常值的影响以及提高模型在稀疏或有噪声数据区域的可靠性来增强鲁棒性。这些模型展示了计算效率和可扩展性，同时提供高精度、物理一致的预测。

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引用次数: 0

Multi-stage interactions on flame stability and NOx emissions in ammonia/methane co-combustion via fuel nitrogen-hydrocarbon separation 氨/甲烷共燃烧中燃料氮烃分离对火焰稳定性和NOx排放的多阶段相互作用

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105870

Yuanping Yang , Tong Si , Qian Huang , Peng Ma , Shuiqing Li

Co-combustion of ammonia with fossil fuels is inherently constrained by the trade-off between flame stability and NO_x control. In our prior work, an innovative fuel nitrogen-hydrocarbon separation concept was proposed to broaden the low NO_x emission window by attenuating radical-driven reaction pathways. However, the influence of multi-stage flame interactions and mixing dynamics on the competing routes of nitrogen conversion remains insufficiently understood. In the present study, these effects are systematically investigated using a two-stage tangential swirl burner, with particular emphasis on their roles in governing flame stability and NO_x formation. Experimental investigations reveal three distinct flame stability regimes governed by ammonia blending ratio (E_NH3): (i) dual-flame stable, (ii) detached ammonia flame, and (iii) pulsating methane flame. Increasing E_NH3 enhances primary flame stability, but leads to a higher tendency for pulsation in the secondary methane flame due to attenuated secondary flow. NO_x emissions exhibit a non-monotonic dependence on the primary equivalence ratio (Φ_pri), with an optimal value around 1.05 achieving 134 to 298 ppm (@ 3.5 % O₂) NO_x emissions and NH₃ slip below 10 ppm. Notably, the influence of Φ_pri on NO_x emissions diminishes progressively as the overall equivalence ratio (Φ_ove) increases from 0.6 to 0.9, thereby remarkably broadening the low NO_x emission window. Spatially resolved NH₂* and OH*chemiluminescence analyses demonstrate that NO_x suppression correlates strongly with reduced overlap between primary and secondary reaction zones. Chemical reactor network analysis confirms that reduced multi-stage mixing suppresses HNO formation by impeding oxidative radical entrainment into ammonia-rich zones. This study fills a critical gap by quantifying how multi-stage mixing dynamics govern the trade-off between flame stability and NO_x emissions in ammonia/methane co-combustion.

氨与化石燃料的共燃烧本质上受到火焰稳定性和NOx控制之间权衡的限制。在我们之前的工作中，我们提出了一种创新的燃料氮烃分离概念，通过减弱自由基驱动的反应途径来扩大低NOx排放窗口。然而，多级火焰相互作用和混合动力学对氮转化竞争路线的影响仍未得到充分的了解。在目前的研究中，使用两级切向旋流燃烧器系统地研究了这些影响，特别强调了它们在控制火焰稳定性和NOx形成中的作用。实验研究揭示了氨混合比（ENH3）控制的三种不同的火焰稳定性机制：(i)双火焰稳定，（ii）分离氨火焰，（iii）脉动甲烷火焰。增加ENH3可以增强一次火焰的稳定性，但由于二次流减弱，导致二次甲烷火焰的脉动倾向增加。氮氧化物排放表现出非单调依赖于初级当量比（Φpri），在1.05左右的最佳值可实现134至298 ppm （3.5% O2）的氮氧化物排放，NH3滑落至10 ppm以下。值得注意的是，随着总当量比（Φove）从0.6增加到0.9，Φpri对NOx排放的影响逐渐减弱，从而显著拓宽了NOx低排放窗口。空间分辨NH2*和OH*化学发光分析表明，抑制NOx与减少主次反应区重叠密切相关。化学反应器网络分析证实，减少多级混合通过阻止氧化自由基携带到富氨区来抑制HNO的形成。本研究通过量化多级混合动力学如何控制氨/甲烷共燃烧中火焰稳定性和NOx排放之间的权衡，填补了一个关键空白。

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引用次数: 0

Combustion and blow-out behavior in a cavity flame holder of Mach 2.5 n-dodecane-fueled scramjet model combustor 马赫数2.5 n-十二烷燃料超燃冲压发动机模型燃烧室空腔火焰架燃烧与爆燃行为

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105834

Shinji Nakaya , Yuki Hirayama , Yutaro Otsuka , Kaito Hirose , Kotaro Nakayama , Kan Kobayashi , Masahiro Takahashi , Sadatake Tomioka , Mitsuhiro Tsue

The supersonic combustion mechanism was experimentally investigated using a Mach 2.5 n-dodecane fueled ramjet/scramjet dual-mode combustor with a cavity flame holder at stagnation pressure of 1021 kPa and a stagnation temperature of 1847 K. Heated n-dodecane was injected from the cavity closeout ramp. Optical diagnostics, including CH* and OH* chemiluminescence and Laser induced breakdown spectroscopy (LIBS), were employed. During steady combustion, the cavity shear-layer stabilized combustion was established autonomously without any assistance of the torch igniter. The local equivalence ratio was measured by moving the breakdown points using a 3-axis high precision motorized stage with measurements of CH* chemiluminescence in the cavity flame holders. Additionally, measurements were performed at fixed positions at 30 Hz as the fuel injection rate increased gradually. The results indicated the intensive OH* chemiluminescence emissions near the lower wall near the closeout ramp during the stable cavity shear-layer combustion. The equivalence ratio in the lower region of the flame was sufficiently rich, exceeding 2, while the flame region with high OH* and CH* signals was stoichiometric or lean. A steep gradient in the equivalence ratio was observed across the flame. During the transient combustion, as the fuel injection rate increased gradually, the equivalence ratio within the cavity increased. Additionally, the equivalence ratio within the cavity was high on the step side and decreases toward the ramp side. Near the flame regions exhibiting strong CH* chemiluminescence signals, the equivalence ratio approached unity. When the flame left the measurement point, the equivalence ratio exceeded 2, showing a substantial gradient across the flame. The flame tip was located near the fuel rich region exceeding 2. The findings of this study provide valuable insights for the design of kerosene-fueled scramjet combustors. Furthermore, the steady cavity flame demonstrated here has potential applications as a piloted flame for staged combustions.

在滞止压力为1021 kPa、滞止温度为1847 K的2.5马赫正十二烷燃料冲压发动机/超燃冲压发动机双模燃烧室中，对超声速燃烧机理进行了实验研究。加热的正十二烷从腔体关闭斜坡注入。光学诊断包括CH*和OH*化学发光和激光诱导击穿光谱（LIBS）。在稳定燃烧过程中，腔剪切层稳定燃烧在没有点火器辅助的情况下自动建立。利用3轴高精度机动台移动击穿点，测量了腔内火焰支架中的CH*化学发光，从而测量了局部等效比。此外，随着燃油喷射速率的逐渐增加，在30 Hz的固定位置进行测量。结果表明：在稳定腔型剪切层燃烧过程中，在关闭斜坡附近的下壁附近有强烈的OH*化学发光发射；火焰下部区域等效比足够丰富，超过2，而具有高OH*和CH*信号的火焰区域则是化学计量或稀薄的。在整个火焰中观察到等效比的陡峭梯度。瞬态燃烧过程中，随着喷油速率的逐渐增大，空腔内当量比增大。此外，腔内等效比在台阶侧高，在斜坡侧降低。在具有强CH*化学发光信号的火焰区域附近，等效比接近于1。当火焰离开测点时，等效比超过2，在火焰上呈现明显的梯度。火焰尖端位于超过2的富燃料区附近。该研究结果为煤油燃料超燃冲压发动机燃烧室的设计提供了有价值的见解。此外，稳定腔火焰演示这里有潜在的应用，作为一种先导火焰分阶段燃烧。

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引用次数: 0

Investigating the use of ammonia- and methanol-diesel blends in reactivity controlled compression ignition mode for marine engines 研究氨和甲醇-柴油混合物在船舶发动机反应性控制压缩点火模式中的应用

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105813

Aneesh Vijay Kale, Harsh Darshan Sapra, Saurabh Kumar Gupta, Reed Hanson, Sage Kokjohn

There is a need to adopt low-carbon fuels such as ammonia and methanol to decarbonize the marine fleet. The higher autoignition temperatures of ammonia and methanol make it challenging to use these fuels in conventional diesel engines. Previous studies have demonstrated that operating a conventional diesel engine in the Reactivity Controlled Compression Ignition (RCCI) mode has the potential to utilize low-carbon fuels without compromising engine performance or emissions. This study comprehensively compares the RCCI engine characteristics when methanol-diesel and ammonia-diesel are used as fuels. Experiments were conducted in a 6.7 L Cummins ISB engine for the methanol-diesel RCCI. A 3D CFD numerical engine model was developed in the Converge software and validated with experimental data. The ammonia-diesel RCCI was studied by replacing the methanol-diesel blend with the ammonia-diesel blend for the same fuel energy. The premixed energy ratio was varied from 5 % to 95 % for the constant fuel energy, keeping all other engine operating parameters the same. Best cases for RCCI combustion were chosen based on maximum gross indicated thermal efficiency and minimum greenhouse gas emissions. The maximum gross indicated thermal efficiency for the methanol-diesel RCCI (obtained by substituting 83 % diesel mass with methanol) was 20 % higher than that of ammonia-diesel RCCI (obtained by substituting 65 % diesel mass with ammonia) and 13 % higher than that of conventional diesel combustion. Overall, this study provides directions on using methanol and ammonia as sustainable fuels for marine engines, selecting the optimal premixed energy ratios to achieve efficient RCCI combustion.

有必要采用氨和甲醇等低碳燃料来使船舶脱碳。氨和甲醇的自燃温度较高，这使得在传统柴油发动机中使用这些燃料具有挑战性。此前的研究表明，在反应性控制压缩点火（RCCI）模式下运行传统柴油发动机，有可能在不影响发动机性能或排放的情况下使用低碳燃料。本文综合比较了甲醇柴油和氨柴油两种燃料下RCCI发动机的特性。实验在6.7 L康明斯ISB发动机上进行，用于甲醇柴油RCCI。在Converge软件中建立了三维CFD数值发动机模型，并用实验数据进行了验证。在相同的燃料能量下，用氨柴油混合物代替甲醇柴油混合物，研究了氨柴油混合物的RCCI。在燃料能量不变的情况下，预混能比在5% ~ 95%之间变化，同时保持发动机其它运行参数不变。RCCI燃烧的最佳案例是根据最大总指示热效率和最小温室气体排放来选择的。甲醇-柴油RCCI（用甲醇取代83%柴油质量获得）的最大总指示热效率比氨-柴油RCCI（用氨取代65%柴油质量获得）高20%，比常规柴油燃烧高13%。总体而言，本研究为使用甲醇和氨作为船用发动机的可持续燃料，选择最佳的预混能比以实现高效的RCCI燃烧提供了方向。

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引用次数: 0

Title Page 标题页

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/S1540-7489(25)00203-2

引用次数: 0

Exhaust emissions point measurements on the secondary stage of an NH3-RRQL system NH3-RRQL系统二级废气排放点测量

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105791

Cristian D. Avila Jimenez , Renee Cole , Jamie Parnell , Mark Peckham , David Wu , Benjamin Emerson

The Rich-Relaxation-Quench-Lean (RRQL) combustion system was recently proposed to increase combustion efficiency in ammonia (NH₃)-fueled gas turbines while reducing nitrogen oxides (NO_x). Success requires precise control of the lean secondary stage, where air oxidizes the remaining fuel from the rich primary stage. However, understanding pollutants distribution across the secondary stage is crucial for designing RRQL systems that minimize NO_x and nitrous oxide (N₂O) emissions. This study experimentally investigates axial and radial distributions of exhaust species across the secondary stage of a lab-scale NH₃-fueled RRQL burner. The burner operated with rich premixed NH₃–air mixtures and employed a secondary air injection geometry of five-4.1 mm diameter holes, selected for its ability to stabilize diffusion-like flames at ϕ_global = 0.85 and premixed-like flames at ϕ_global = 0.60. A fused quartz probe enabled gas sampling at multiple locations upstream within, and downstream from the secondary injection plane. At ϕ_primary = 1.13, results show that NO is formed slightly upstream the air injection plane, whereas NO₂ is rapidly produced downstream and NH₃ and N₂O slip through the walls between the jets. A notable fraction of total NOₓ was found to be NO₂, post-secondary combustion zone, underscoring the need to consider NO₂ explicitly in overall emissions assessments of staged NH₃ combustion systems. Decreasing ϕ_global to 0.60 reduces the overall emissions, highlighting the importance of premixed-like combustion in pollutants mitigation in the secondary stage. Although similar trends were observed at ϕ_primary = 1.15, higher NO_x levels resulted from increased NH₃ availability. However, thermal insulation of the combustor walls effectively reduced NH₃ slip, likely due to enhanced non-oxidative cracking, enabling sub-10 ppm N₂O emissions. These findings emphasize the importance of simultaneous primary and secondary stage tuning, reduction of heat losses, and the promotion of premixed-like combustion through adequate jet momentum for optimal performance of NH₃-fueled RRQL systems.

富松弛-淬灭-贫（RRQL）燃烧系统最近被提出，以提高氨（NH3）燃料燃气轮机的燃烧效率，同时减少氮氧化物（NOx）。成功需要精确控制稀薄的二级，在那里空气氧化从丰富的一级剩余的燃料。然而，了解污染物在整个二级阶段的分布对于设计RRQL系统以最大限度地减少氮氧化物和氧化亚氮（N2O）的排放至关重要。本研究通过实验研究了实验室规模的NH₃燃料RRQL燃烧器二级排气物质的轴向和径向分布。燃烧器使用丰富的预混nh3 -空气混合物，并采用5 -4.1 mm直径孔的二次空气喷射几何形状，选择该形状是因为它能够稳定扩散型火焰在ϕglobal = 0.85和预混型火焰在ϕglobal = 0.60时。熔融石英探头可以在二次注入面上游和下游的多个位置进行气体采样。在ϕprimary = 1.13时，NO在喷气面上游形成，而NO2在喷气面下游迅速生成，NH3和N2O通过射流之间的壁面滑动。总NOₓ的显著部分被发现是NO2，后二次燃烧区，强调需要在分级NH₃燃烧系统的总体排放评估中明确考虑NO2。将全球ϕ值降低至0.60可减少总排放量，突出了在二级阶段减少污染物的预混式燃烧的重要性。尽管在ϕprimary = 1.15时观察到类似的趋势，但NH₃可用性的增加导致了更高的NOx水平。然而，燃烧室壁的隔热层有效地减少了NH₃滑动，可能是由于增强的非氧化性开裂，使N2O排放低于10 ppm。这些发现强调了同时调整一级和二级的重要性，减少热损失，并通过足够的射流动量促进预混燃烧，以实现nh3燃料RRQL系统的最佳性能。

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引用次数: 0

Kinetic study of ozone-sensitized low- and high-temperature oxidation of dimethyl carbonate 臭氧敏化碳酸二甲酯低温氧化动力学研究

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105788

Bowen Liu, Rui Bo, Hao Zhao

The low- and high-temperature oxidation of dimethyl carbonate (DMC), a key electrolyte component in lithium-ion batteries (LIBs), was carried out with ozone (O₃) addition by using an atmospheric pressure Jet Stirred Reactor (JSR) from 400 to 1200 K. Kinetic analysis of DMC oxidation was conducted using the coupled Plug Flow Reactor-Perfectly Stirred Reactor (PFR-PSR) module. Without O₃ addition, the oxidation of DMC initiated at 950 K with no low-temperature reactivity. However, the low-temperature chemistry of DMC was observed from 450 K with O₃ addition, and O₃ significantly enhanced the low-temperature reactivity of DMC. Two kinetic models with incorporating the O₃ sub-model were employed and predicted the experimental data reasonably well, even though slightly overpredicted DMC oxidation above 550 K under the fuel-lean condition. Furthermore, a temperature-independent coefficient (TIC) behavior of DMC with O₃ addition was observed between 600 and 950 K both in experiments and simulations, which was associated with the pyrolysis of DMC radicals to CH₂O and CO₂, and then to CO, while the low-temperature oxidation pathway through 1^st and 2^nd O₂ addition and CO oxidation to CO₂ was negligible. The fast pyrolysis reaction rates of O₃ and DMC radicals, such as CH₃OC(=O)OCH₂ and CH₃OC(=O), explain the TIC behavior in the pathway and sensitivity analyses. This work used O₃ to mimic the oxidizing environment in LIBs by providing active atomic oxygen, and implied that the early degradation of LIBs could be attributed to the low-temperature oxidation of DMC with reactive oxygen species. It provides kinetic evidence for a higher level of CO₂ and a lower level of CO in the initial stage of the thermal runaway in LIBs.

采用常压喷射搅拌反应器（JSR），在400 ~ 1200 K的温度下，对锂离子电池（LIBs）的关键电解成分碳酸二甲酯（DMC）进行了臭氧（O3）的低温氧化。采用塞流反应器-完全搅拌反应器（PFR-PSR）耦合模块对DMC氧化过程进行动力学分析。在不添加O3的情况下，DMC在950 K时开始氧化，无低温反应性。然而，在450 K时，加入O3观察到DMC的低温化学反应，O3显著增强了DMC的低温反应活性。采用了两个包含O3子模型的动力学模型，对实验数据进行了较好的预测，尽管在低燃料条件下对550 K以上DMC氧化的预测略高。此外，在600 ~ 950 K范围内，实验和模拟均观察到O3加入后DMC的温度无关系数（TIC）行为，该行为与DMC自由基热解生成CH2O和CO2，然后生成CO有关，而通过第1次和第2次O2加入以及CO氧化生成CO2的低温氧化途径可以忽略不计。O3和DMC自由基CH3OC(=O)OCH2和CH3OC（=O）的快速热解反应速率解释了TIC在通路和敏感性分析中的行为。本研究使用O3模拟LIBs中的氧化环境，提供活性氧原子，并暗示LIBs的早期降解可能归因于DMC与活性氧的低温氧化。这为LIBs热失控初期较高水平的CO2和较低水平的CO提供了动力学证据。

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引用次数: 0

Structure and nitrogen oxide emissions of confined turbulent hydrogen jet flames 受限湍流氢射流火焰的结构与氮氧化物排放

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105851

T.L. Howarth , S. Nerzak , P. Gruhlke , J.T. Lipkowicz , L. Panek , S. Pfadler , M. Gauding , H. Pitsch

In this work, a database analysis of three-dimensional direct numerical simulations using detailed chemistry is presented considering a turbulent lean premixed hydrogen/air round jet flame at elevated pressure and temperature (

ϕ = 0.5, T_{u} = 530 K, p = 8 atm

), subject to different levels of domain confinement by solid walls. It is shown that for sufficiently small domain sizes, a coherent recirculation zone is present as expected; however, this does not affect the flame structure, consistent with experiments of attached hydrogen flames. Examination of velocity statistics indicates that, while both turbulent kinetic energy and Reynolds shear stresses increase with increasing domain size, these changes occur sufficiently far away from the flame. Each of the flames experiences the same level of mean shear, leading to the same flame structure. Despite identical turbulence-flame interactions between cases, nitrogen oxide (NO) emissions from the flames are observed to be different. For flames with recirculation zones comparable in size to the flame height, the superadiabatic temperatures caused by intrinsic flame instability are retained within the recirculation zone. Often, residence times in the post-flame are too short for locally elevated temperatures to have a significant impact on thermal NO formation. However, when these higher temperatures are coupled with the long fluid residence time in the recirculation zone, despite lower global residence times, this analysis shows that NO emissions from the flame can be enhanced.

在这项工作中，采用详细的化学方法对三维直接数值模拟进行了数据库分析，考虑了在高压和高温下（φ =0.5,Tu=530K,p=8atm）湍流稀薄预混氢/空气圆形射流火焰，受到固体壁不同程度的域限制。结果表明，在足够小的畴尺寸下，像预期的那样存在一个相干再环流区；然而，这并不影响火焰的结构，与附着氢火焰的实验一致。速度统计表明，虽然湍流动能和雷诺剪应力都随着区域尺寸的增加而增加，但这些变化发生在离火焰足够远的地方。每个火焰经历相同的平均剪切水平，导致相同的火焰结构。尽管不同情况下的湍流-火焰相互作用相同，但观察到火焰的氮氧化物（NO）排放是不同的。对于尺寸与火焰高度相当的再循环区的火焰，由火焰固有不稳定性引起的超绝热温度保留在再循环区内。通常，在火焰后的停留时间太短，局部升高的温度对热NO的形成产生重大影响。然而，当这些较高的温度与较长的流体在再循环区的停留时间相结合时，尽管总体停留时间较短，但该分析表明，火焰的NO排放可能会增加。

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引用次数: 0

Microgravity flame extinction induced by a moving air vortex ring 运动空气涡旋环诱导的微重力火焰熄灭

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105825

Sainan Quan , Feng Zhu , Jinglong Lyu , Caiyi Xiong , Xinyan Huang , Shuangfeng Wang

With the growth of outer space exploration missions, a safe, effective and clean fire extinguishing in microgravity spacecraft environment is critical. This paper explores the microgravity flame extinction dynamics induced by a moving air vortex ring. Tests were conducted both on the ground and in microgravity by a drop tower for comparison. An electromagnetic piston-tube system was designed to produce well-controlled air vortex ring to extinguish candle flames with different heat release rates (HRRs). We found a linear extinction boundary correlating the flame HRR with the Reynolds number and characteristic thickness of vortex ring. The flame extinguishing efficiency of air vortex ring in microgravity is 30 % higher than that on the ground. To explain the underlying mechanism, the flame stretch rate that accounts for the unsteady effect, i.e., the competition between external disturbance and flame self-stabilization, was examined. The absence of gravity and buoyancy has a minimum effect on the vortex ring but reduces the oxygen supply and flame diffusion, thereby the flame in microgravity is more vulnerable to vortex ring disturbance. The power of generating a vortex ring is 2–3 orders of magnitude lower than the HRR of flame that it can extinguish, and such a power requirement can be further reduced by 20–30 % in microgravity. This work reveals limiting conditions of vortex ring-induced flame extinction in microgravity and helps design future clean firefighting system for space travel.

随着外空探测任务的不断增多，安全、有效、清洁的航天器微重力环境灭火至关重要。本文研究了运动空气涡旋环引起的微重力火焰熄灭动力学。试验在地面和微重力条件下通过一个跌落塔进行比较。设计了一种电磁活塞管系统，以产生可控的空气涡流环来扑灭不同放热速率的蜡烛火焰。得到了火焰HRR与旋涡环的雷诺数和特征厚度之间的线性消光边界。空气涡旋环在微重力条件下的灭火效率比在地面条件下的灭火效率高30%。为了解释其潜在的机理，研究了考虑非定常效应的火焰拉伸率，即外部扰动与火焰自稳定之间的竞争。没有重力和浮力对旋涡环的影响很小，但会减少供氧和火焰的扩散，因此微重力下的火焰更容易受到旋涡环的扰动。产生旋涡环的功率比其扑灭火焰的HRR低2-3个数量级，在微重力条件下可进一步降低20 - 30%的功率要求。这项工作揭示了微重力条件下涡环灭火的极限条件，为未来太空旅行清洁灭火系统的设计提供了依据。

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